Electro-hydraulic servovalve



y 1963 w. G. HOLZBOCK 3,099,280

ELECTRO-HYDRAULIC SERVOVALVE Filed Nov. 16, 1960 3 Sheets-Sheet l INVENTOR. WERNER G. HOLZBOCK ATTY,

July so, 1963 w. G. HOLZBOCK 3,099,280

ELECTRO-HYDRAULIC SERVOVALVE Filed Nov. 16, 1960 3 Sheets-Sheet 2 Z393 J08 J10 100 104 J INVENTOR.

WERNER G. HOLZBOCK ATTY.

y 1963 w. G. HOLZBOCK 3,

ELECTRO-HYDRAULIC SERVOVALVE Filed Nov. 16. 1960 3 Sheets-Sheet 3 INVENTOR. WERNER G. HOL 2 50 K W JMQA ATTY.

ite States hce 3,099,280 ELECTRO-HYDRAULIC SERVOVALVE Werner G. Holzbock, Birmingham, Mich, assignor to Vickers Incorporated, Troy, Mich., a corporation of Michigan Filed Nov. 16, 1960, Ser. No. 69,754 10 Claims. (Cl. 137-83) This invention relates to a single stage electro-hydraulic servovalve for the control of fluid flow and pressure.

In my co-pending patent applications, Serial No. 34,203, filed June 6, 1960, which issued as Patent No. 3,064,682 on November 20, 1962, and Serial No. 48,129, filed August 8, 1960, now abandoned, are disclosed servovalves having objectives in common with the objectives of the subject invention. However, the subject invention distinguishes thereover in certain details of structure which may be considered improvements over the structure of the co-pending applications. Like the devices of the copending applications, the device of the subject invention utilizes the jet pipe principle of operation, but differs from jet pipe servovalves of the prior art in many important respects, such as for example; it has no bearings, sharp internal bends, which produce pressure losses due to hydraullic turbulence, are avoided, freedom from silting and clogging is made possible, more compactness is achieved, and, coupled with the latter, is reduction in size for comparable operating range.

The main object of this invention is to provide a single stage electro-hydraulic servovalve which utilizes the jet pipe principle of operation in a novel and improved manner.

A more specific object is to provide an electro-hydraulic servovalve wherein bearings are eliminated.

Still another object of the invention is to provide an electro-hydraulic servovalve wherein the effect of hydraulic turbulence is minimized.

Another object of the invention is to provide an electro-hydraulic servovalve wherein virtually frictionless operation is achieved.

A further object is to provide an electro-hydraulic servovalve wherein freedom from silting and clogging is provided.

Still another object is to provide an electro-hydraulic servovalve wherein great compactness is provided coupled with reduction in size for comparable operating range.

These and further objects and features of the invention will become more apparent from the following description and accompanying drawings wherein:

FIG. 1 is a vertical section view of an electro-hydraulic servovalve embodying the principles of the invention;

FIG. 2 is a section view generally as seen along line 22 in FIG. 1;

FIG. 3 is a vertical section view of a modified form of electro-hydraulic servovalve embodying the principles of the invention;

FIG. 4 is a section view generally as seen along line 4-4 in FIG. 3;

FIG. 5 is a vertical section view of another modified form of electro-hydraulic servovalve embodying the principles of the invention; and

FIG. 6 is a section view generally as seen along line 6--6 in FIG. 5.

Referring now to the drawings and more particularly FIGS. 1 and 2, numeral 10 identifies an electro-hydraulic servovalve, including a main block, or housing 12, to which is affixed an assemblage having a magnet cover plate 14, and a magnet housing 16. The housing .12, which may be substantially cubic in form, has a circular recess 18 provided on a side surface, while on the opposite surface is provided a circular recess 20. A bore, or passageway 22, is centrally arranged in the housing 12,

and extends between the circular recesses 18 and 20. A duo-diameter cavity, or opening '24 extends upwardly from the bottom of the housing 12, and is adapted to receive a pipe fitting (not shown) for receipt of a hose connected to a source of pressurized hydraulic medium, such as oil. A threaded outlet opening 28 extends inwardly from the rear of the housing 12, and is adapted to receive a pipe fitting (not shown) for receipt of a hose for conduction of spent hydraulic fluid to a reservoir from where it is pumped under pressure to the inlet 26 in a known manner. Arranged at the lower extremity of the inlet opening 26 is a reduced diameter passageway 30 which intersects the passageway 22, while a passageway 32 is formed to interconnect the opening .24 with the opening 28.

Slidably positioned within the bore '22 is a jet spool 34, which is cylindrical in shape, and has a portion removed at the mid-region to provide an elongated notch, or recess 36. Extending upwardly from the recess '36 is an opening 38 which terminates in a reduced diameter opening, or hole 40, the latter serving to jet pressurized medium from passageway 30 downwardly through the jet spool opening 38, and recess 36.

Secured within the opening 24 by fastening means such as screws 42, is a jet stream receptor means in the form of a distributor block 44, which has a cylindrical projection 46 adapted for placement within the cavity 24, and in spaced relation to the walls thereof. A pair of passageways 4-8, 50 are formed in the distributor block 44, the upper extremity of each passageway providing ad jacent orifices, or ports 52, 54 respectively, located on the upper surface of the projection 46, and with the center of each port lying in a plane coincident with the longitudinal centerline of the jet spool 34. The lower extremity of each pasageway 48, 50, leads to threaded openings 53, '55 respectively, extending upwardly within the distributor block 44. The openings 53, 55 are each adapted to receive pipe fittings (not shown) for conduction of hydraulic pressure medium through a pipe, or hose leading to an activating mechanism, such as a cylinder and piston assembly, driven by the servovalve '10. It will be seen that longitudinal movement of the jet spool 34 will cause the jet nozzle hole 40 to direct a jet stream of pressurized hydraulic medium toward one or the other of ports 52, 54. In such manner, the recovered hydraulic pressure within the openings 53, 55, which may be between to percent of supply pressure, will depend upon the position of the jet spool 34 relative to the ports 52, 54. It is to be noted that the large diameter of the flow passages practically eliminates all possibilities of silting or clogging.

The jet spool 34 is supported for sliding movement within the bore 22, by a pair of hanger members 56, each of which is arranged toward the ends of the jet spool, said hanger members being formed of fiat strip, or wire. The members 56 each pass through a vertical passageway, or hole 58 in the housing 12, and are secured at their upper end to an adjusting head 60, having screw means 62 alfording vertical positioning of the jet spool within the passageway 22. While the supporting arrangement for the jet spool 34 will result in some vertical displacement of the spool during longitudinal movement, such will be of a very small amount which may he provided for by the clearance between the jet spool and the enclosing passageway. Cover means 64, may be removably afiixed to the housing 12 so that the adjusting heads 60 are pro arranged groove on one surface for support of a pin 70. The latter is adapted to secure one end of a tension spring 72 which extends through the hole 68 and is afiixed to the end of the jet spool 34. An adjusting screw 74 is adapted to extend through the stop plate 66 a predetermined distance to regulate the maximum leftward travel of the jet spool 34. A bolt, or stud means 76 is axially secured to the other end of the jet spool 34, which bolt means is arranged for support of an elcctrO-magnctrc means in the form of a voice coil assemblage 78. A bolt, or screw 80 is arranged to extend through an opening 82 formed in the voice coil assemblage, and to be screwed into the inner surface of the circular recess 18; by adjusting the position of the head of the screw 86 relative to the voice coil assemblage, the maximum rightward travel of the voice coil assemblage, and hence, that of the jet spool 34, may be controlled.

The voice coil assemblage 78 includes windings 84 arranged for axial movement within a circular gap 86 provided between a magnet center piece 83 and the magnet cover plate 14. The magnet center piece 88 is afiixed to a permanent magnet 90 which is secured within the magnet housing 16. It will be seen that with the above described arrangement, a magnetic circuit is provided which passes from the magnet 90, through the magnet center piece 88, across the circular gap 86, through the magnet cover plate 14, and through the magnet housing 16 back to the magnet 90. In such manner, a constant flux field is provided in the circular gap 86.

The voice coil assemblage 78 includes two windings; a signal winding and a bias winding, which are adapted to accommodate input signals from 30 milliwatts to 5 watts. The signal winding functions to longitudinally position the jet spool 34 in accordance with electrical input signal, while the bias winding functions to attain a center position of the jet spool relative to the ports 52 and 54 for any desired base value of the control signal that is applied to the signal winding. The bias signal remains constant, while the control signal may vary above or below a given base value, thus positioning the jet sp l 34 against the force of the tension spring 72. The spring rate determines the amount which the jet spool moves for a given increment of control signal; it thus determines the range. The position of the jet spool 34 will be proportional to the input signal. The bias winding is connected to a constant DC voltage source. Current flow through the windings is adjustable by a potentiometer, or similar method which makes fast zeroing of the servovalve possible. 'I he potentiometer (not shown) may be mounted directly upon the exterior of the servovalve. instead of applying a constant current to the bias Winding, a feed back signal from the final control element (not shown) may be used.

It is customary to have a spring determine both bias and range in many electro-hydraulic servovalves. The bias is then obtained by the necessary pre-compress ron or pre-extension of the spring. This limits such devices to comparatively large ranges, i.e., large signals for a given movement of the piston. The reason for such limitation is that for practical considerations, comparatively large spring rates are used, otherwise the spring would be too long if it is to provide the required pretension or precornpression. The arrangement of the servovalve of the 1nvention, provides a constant-not a springsigna1 force, hence, permits operation with very small ranges.

A cover plate 92 is affixed to the housing 12 to enclose the circular recess 20. In addition, means (not shown) including a terminal block, are arranged for the electri cal connection of the servovalve as required.

A modified form of electro-hydraulic servovalve embodying the principles of the invention is shown in FIGS. 3 and 4. While the modified Efiorm of servovalve exhibits the same desirable characteristics of the serv-ovalve above described, it difiers therefrom in certain structural details,

particularly in the structure of the jet spool, or equivalent thereof.

Referring now to the drawings, the numeral identifies a servovalve including a main body portion, or housing 1102, to which is afiixed a magnet cover plate 104, which has an end cover plate 106 secured thereto. The housing 162 is formed with :a cavity 108, enclosed at the upper end by a cap 110, which has an integral protuberance 112 extending downwardly in the cavity 108. A threaded inlet opening 114 formed in the protuberance 112, is adapted to receive a pipe fitting (not shown) for receipt of a hose connected to a source of pressurized hydraulic medium, such as oil. A collar means 116 secured to the exterior of the protuberance 112, is adapted to support a pair of suspension springs 118, on one side, and a pair of threaded members, such as studs 120, on the opposite side. The lower extremity of the pro-tuberance 112 has a rounded surface 122 against which a jet nozzle piece 124 is arranged to slide. The nozzle piece 124 is secured to a bar 126 supported upon one end of a flat spring 128, the other end of the spring being secured to a clamping assemblage 136 which is aflixed to the ends of the suspension springs 118. A strap means 132 is adjustably supported by the studs 126, and serves as an end support for a tension spring 134, the other end of the spring 134 being secured to the bar 126. The protuberance 112 is provided with a hole 136 at its lower end, which is arranged in alignment with a jet nozzle defined by a hole 138 formed in the jet nozzle piece 124, the latter being arranged over holes 146 and 142, formed in the bar 126 and flat spring 128 respectively.

A pair of threaded outlet holes 144 and 146 are formed in the lower portion of the main housing 102, and are adapted to receive pipe connections (not shown) for conduction of pressurized hydraulic medium through a pipe, or hose leading to an actuating mechanism to be controlled by the servovalve 100. At the upper end of each hole 144 and 146 are passageway means 148 and 150* respectively, having the ends of receiver pipes 152 and 154 respectively secured therein by means such as welding or soldering. The upper ends of the pipes 152 and 154 provide orifices, which are in equal spaced relation to the flat spring 128, and the center of each pipe is in a plane coincident with the plane of movement of the jet nozzle 138. In such manner, movement of the jet nozzle piece 124 will direct a jet stream of hydraulic fluid into one or the other of the receiver pipes 152, 154, according to its relative position thereto.

A threaded outlet opening 156, is arranged in the side of the main housing 102, and is adapted to receive a pipe fitting (not shown) for receipt of a hose for conduction of spent fluid from the cavity 108 to a reservoir, from where it is pumped under pressure to the inlet 114 in known manner.

An electro-magnet arrangement, similar in function and structure to that described in connection with the first embodiment herein, includes a coil assemblage having a pair of windings 158 arranged for movement in a circular gap 166 formed between a magnet center piece 162, and an inner circular surface of the magnet cover plate 104. The center piece 162 is secured to the end of a permanent magnet 164 which is affixed to the inside Wall of the cover plate 104. The coil assemblage is supported upon a rod 166 which extends through the center piece 162, magnet 164 and the end of the cover plate 104. One end of the rod 166 is connected to the clamping assemblage 130, while the other end is secured to the free end of a suspension spring 168, the other end of the spring being aflixed to a clamping block 170 secured to an outer surface of the cover plate 104. A strap 172, extending downwardly from the rod 166, has an end slot 174, through which extends an adjustment screw 176 threaded into the cover plate 106. The head of the screw 176 limits the maximum leftward movement of the coil assemblage. An adjustment screw 178 is arranged to project into the enclosure provided by cover plate 106, for abutting relationship with the end of the strap 172, to thus limit maximum rightward movement of the rod 166, hence, such rightward movement of the coil. A plate 180 may be arranged to cover the holes for adjusting screws .176 and 178. A covered recess or terminal box 182 may be provided in the main housing 102 for electrical connections as required.

A second modified form of electro-hydraulic servovalve embodying the principles of the invention, illustrated in FIGS. 5 and 6, is similar in function and structure to the embodiment of the FIGS. 3 and 4 servovalve, however, it differs mostly in the manner of suspending the jet nozzle piece.

Referring to FIG. 5, the numeral 190 identifies a servovalve which includes a main body portion, or housing 192 to which is aifixed a magnet housing 194, and a cover, or cap 196 secured to the housing by bolt means 197. The cap 196 has a protuberance 198 which extends downwardly in a cavity 200 formed in the housing 194. A threaded opening 202 formed in the protuberance is adapted to receive a pipe fitting (not shown) for receipt of a hose connected to a source of pressurized hydraulic medium. A spring base plate 204 is secured to the prortubcrance for support of suspension springs 206, one of each being arranged on opposite sides of the protuberance. The lower end of each spring 206 supports a nozzle yoke 208, adapted to support a nozzle plate 210 in sliding engagement with the bottom of the protuberance. The nozzle plate 210 has a hole 212, which serves to jet a stream of hydraulic fluid from the opening 202 via a hole 214 formed in the inlet opening 202.

A pair of threaded outlet holes 216 and 218 are formed in the lower portion of the housing 192, and are adapted to receive pipe connections (not shown) for conduction of pressurized hydraulic liquid medium through a pipe or hose leading to an actuating mechanism controlled by the servovalve. At the upper end of each hole 216 and 218 are passageway means 221 and 223 respectively, having the ends of receiver pipes 220 and 222 respec tively, secured therein by means such as welding, or soldering. The upper ends of the pipes 220 and 222 form orifices which are arranged in equal spaced relation to the nozzle yoke 208, and the center of each pipe is in a plane coincident with the plane of movement of the jet nozzle 138. In such manner, the jet nozzle 138 will direct a jet stream of hydraulic fluid into one or the other of the receiver pipes 220, 222, according to its relative position thereto. A threaded outlet opening 224 is arranged in the side of the main housing 192, and is adapted to receive a pipe fitting (not shown) for receipt of a hose for conduction of spent fluid from the cavity 200 to a reservoir, from where it is pumped under pressure to the inlet 202, in known manner.

A stop plate 226 afixed to the nozzle yoke 208 may engage an adjustment screw 228 to limit maximum leftward movement of the nozzle yoke, and engage an adjustable stop 230, which is mounted upon a screw 23-2, to limit maximum rightward movement of the nozzle yoke.

An electro-magnet assembly 233 similar in structure and function to that described in connection with the two other embodiments herein, includes a coil assemblage having a pair of windings 23'4 arranged for movement in a circular gap 236, formed between a magnet center piece 238, and an inner circular surface of the magnet housing 194. The center piece 238 is secured to the end of a permanent magnet 240, which is afiixed to the inside wall of the magnet housing 194. The electromagnet assembly 233 includes a bobbin plate 242 which is supported upon a shaft member 244 threadably secured to the nozzle yoke 208. A tension spring 246 is positioned within an opening 248 formed in the magnet center piece 238, and magnet 240. One end of the spring 246 is affixed to an adjusting screw 250 mounted in a nut 252 arranged on the end of the magnet 240'. A removable cap 254 is threadably supported in the magnet housing 194, which cap protects the adjusting screw against dirt and unintentional disturbance. A covered recess 256 is provided in the side of the housing 192, to accommodate electrical connections, as required.

From the descriptions of the three embodiments set forth herein, it will be seen that while each differs in certain details of structure, each functions in substantially the same way to achieve the objectives of the invention.

The foregoing description has been given in detail without thought of limitation since the inventive principles involved are capable of assuming other forms without departing from the spirit of the invention or the scope of the following claims.

What is claimed is:

1. An electro-hydraulic servovalve comprising in combination a housing formed to provide a cavity, a cover for said cavity including a protuberance extending into the cavity and serving as a pressurized hydraulic fluid inlet means, said protuberance being formed with an opening at its lower extremity, a jet nozzle arrangement positioned in said cavity and including a nozzle piece maintained in slidable engagement with the bottom of said proturberance, said nozzle piece being for-med to provide a hole which is maintained over said opening in all positions of the nozzle piece, a jet stream receiver means positioned in said cavity and having a pair of orifice means adapted to selectively receive the jet stream of hydraulic fluid from said nozzle piece in accordance with the position of the nozzle piece relative to said orifices, a suspension means for the nozzle piece including flat springs in parallel arrangement, and an electro-magnetic means adapted to provide sliding movement of the nozzle piece irr accordance with an electrical signal fed into the servovalve.

2. An electro-hydraulic servovalve according to claim 1, wherein an adjustable spring means is arranged to resistijiovement of the nozzle piece caused by said electromagnetic means.

3. An electro-hydraulic servovalve according to claim 2, wherein said orifice means are defined by the ends of pipe means which extend into said cavity.

v 4. An electro-hydraulic servovalve according to claim 3, wherein said fiat springs are positioned on each side of said protuberance.

5. An electro-hydrauli-c servovalve according to claim 3, wherein said iiat springs are positioned on each side of said electro-magnetic means.

6. An electro-hydraulic servovalve comprising in combination a housing formed to provide a cavity, said housing being formed to provide a bore, a jet spool slidably arranged in said bore, a pair of hanger members each of which is affixed to said jet spool near an end thereof, said housing being formed to provide a pressurized hydraulic medium inlet having a passageway leading into said bore, said jet spool being formed to provide a hole in axial alignment with said passageway which hole will form a jet stream, a jet stream receiver means positioned in said cavity and having a pair of passageways the ends of which form orifices in equal spaced relation to said jet spool hole, the axis of said orifices being in alignment with longitudinal movement of said jet spool hole, an electromagnetic means for moving said jet spool in one direction in response to an electrical signal fed into the servovalve, and a spring means arranged to resist movement of the jet spool caused by the electro-magnetic means.

7. An electro-hydraulic servovalve according to claim 6, wherein said hanger members are flat springs.

8. An electro-hydraulic servovalve according to claim 7, wherein said hanger members are adjustable along their longitudinal axis.

9. In an ele-ctro-hydraulic servovalve, a housing formed to provide a cavity, a jet nozzle arrangement positioned in said cavity and including, an elongated slidable memher formed to provide a uniform diameter opening the axis of Which is normal to the longitudinal axis of the slidable member, said opening being arranged to develop a jet stream of pressurized medium as it passes through the slidable member in a unidirectional manner, a jet stream receiver means positioned in said cavity and formed to provide a receiving orifice for receiving the jet stream from the slida-ble member and a passageway means associated with said receiving orifice for conducting pressurized fluid out of the servovalve, and means to provide movement of said slidable member in response to a control signal fed to the servovalve.

10. In an electro-hydraulic servovalve, a housing formed to provide a cavity, a jet nozzle arrangement positioned in said cavity and including, an elongated slidable member formed to provide a uniform diameter opening the axis of which is normal to the longitudinal axis of the slida-ble member, said opening being arranged to develop a jet stream of pressurized medium as it passes through the slidable member in a unidirectional manner, a jet stream receiver means positioned in said cavity and formed to provide a receiving orifice for receiving the jet stream from the slidable member and a passageway means associated with said receiving orifice for conducting pressurized fluid out of the servovalve, a suspension means for said slidable member including an elongatedflexible member disposed at each end of the slida b le member and adapted to allow longitudinal movement of the slida'ble member, and means to provide movement of said slida-ble member in response to a control signal fed to the servovalve.

References Cited in the file of this patent UNITED STATES PATENTS \2,672,150 Benedict et al- Mar. 16, 1954 2,904,066 Callender Sept. 15, 1959 2,916,016 Finvold Dec. 8, 1959 2,930,389 Bowditch Mar. 29', 1960 2,960,995 Hague Nov. 22, 1960 2,969,079 Callender Jan. 24, 1961 1 FOREIGN PATENTS Germany Jan. 11, 1933 

9. IN AN ELECTRO-HYDRAULIC SERVOVALVE, HOUSING FORMED TO PROVIDE A CAVITY, A JET NOZZLE ARRANGEMENT POSITIONED IN SAID CAVITY AND INCLUDING, AN ELONGATED SLIDABLE MEMBER FORMED TO PROVIDE A UNIFORM DIAMETER OPENING THE AXIS OF WHICH IS NORMAL TO THE LONGITUDINAL AXIS OF THE SLIDABLE MEMBER, SAID OPENING BEING ARRANGED TO DEVELOP A JET STEAM OF PRESSURIZED MEDIUM AS IT PASSES THROUGH THE SLIDABLY MEMBER IN A UNIDIRECTIONAL MANNER, A JET STREAM RECEIVER MEANS POSITIONED IN SAID CAVITY AND FORMED TO PROVIDE A RECEIVING ORIFICE FOR RECEIVING THE JET STREAM FROM THE SLIDABLE MEMBER AND A PASSAGEWAY MEANS ASSOCIATED WITH SAID RECEIVING ORIFIC FOR CONDUCTING PRESSURIZED FLUID OUT OF THE SEROVALVE, AND MEANS TO PROVIDE MOVEMENT OF SAID SLIDABLE MEMBER IN RESPONSE TO A CONTROL SIGNAL FED TO THE SERVOVALVE. 